Many individuals have a skin complexion which does not tan readily on exposure to sun light. Others achieve a tan only with great discomfort and possibly adverse effects to the skin due to exposure to the suns rays. Yet attainment of a tan by many individuals is highly desired for cosmetic and other reasons, especially if this can be accomplished without the usual exposure to the sun.
In other instances, individuals who tan with difficulty may desire to extend the life of a naturally acquired tan without re-exposure to the sun. Also, a skin tan may be desired when weather conditions do not permit the Usual exposure to the sun in order the acquire a tan.
Acquisition of a natural tan by exposure to the sun, however, may be almost impossible for those very light skinned persons who tend to burn rather than tan. In addition, the deleterious effects of excessive exposure to sunlight are becoming more generally recognized.
One of the most common methods for artificially inducing a suntan is to subject the body to the rays of an ultraviolet ray lamp. While this induces a tan, it has many of the same disadvantages as tanning by the sun since many of the deleterious effects of sunlight are due to its ultraviolet radiation component. For instance, the increasing incidence of skin cancer has been attributed to increased exposure to ultraviolet radiation from the sun.
It is known in the art to induce an artificial tan by applying dihydroxyacetone ("DHA") to the human skin by a suitable vehicle or base. Darkening of the human skin occurs within about 2-24 hours after applying a suitable composition containing DHA as the active agent. See U.S. Pat. No. 2,949,403.
While DHA has been widely commercialized as a skin tanning agent, formulations containing DHA suffer from a number of deficiencies. A particular disadvantage is the time required to produce the desired tanning effect. A further disadvantage is that the tan imparted by DHA readily is washed off the skin. A need therefore exists for skin tanning formulations which more quickly produce the desired tanning effect. A further need exists for skin tanning formulations which are less readily be removed from the skin.